The burden of atherosclerotic vascular disease is immense among adult Americans, contributing to about 800,000 deaths per year. Chronic total occlusions (CTO) are the riskiest, most challenging, and least successful of these vascular lesions to treat with traditional stenting or endovascular devices. Procedural complexity and failure with CTO's are attributed to the lesion structure, which includes a fibrous calcific plaque on the proximal entry side of the lesion, and an irregular micro-lumen spanning its length. Passing a guidewire across this lesion is challenging, as the lateral view provided by 2D fluoroscopic imaging does not directly identify the ?mouth?/entry to the lumen. The flexible tips of the guidewires bend due to multiple-impacts with stiff lesions, increasing the technical challenge with each additional attempt. Even successful procedures are time-consuming, involve chance, require prolonged patient and physician exposure to radiation and use excessive amounts of contrast. This clinical challenge is well recognized in the community. Breaking the calcium with mechanical vibrations or drilling was adopted by several, but the need for a large bore tip to house such mechanical components makes it applicable only in larger vessels. In addition, the debris resulting from such an approach carries the risk of ischemia or stroke in the distal organs. Since endovascular approaches are increasingly utilized over surgical bypass of CTO's, there is an urgent need to develop new technologies to meet this critical need! Thus, the overall goal of this project is to develop a novel steerable guidewire with a miniature forward- viewing ultrasound (US) transducer to enable real-time image-guided CTO traversal. We will address three specific aims ? Sp. Aim 1: Design and develop a robotically steerable, 0.014? diameter guidewire (0.355 mm) system that can accommodate a .350 mm x .350 mm US transducer at its tip and can be steered with image feedback from the transducer. Sp. Aim 2: Design and build a forward-looking transducer for the robotically steerable guidewire and an algorithm to reconstruct an image of the encountered occlusion. Sp. Aim 3: To iteratively optimize the US-steerable guidewire design using 3D printed patient-specific models of CTO's, realistic human cadaver limbs with CTO, and a live animal model of CTO's. This project is innovative on several fronts. It represents the first use of intravascular steerable robotic guidewire capable of forward looking US imaging and image-guided navigation through vasculature and occluded vessels. The ability to steer, visualize and navigate the guidewire is highly novel and will eventually result in improvement of clinical workflow and patient treatment outcomes. This highly interdisciplinary project combines expertise in medical robotics, US imaging, pulsatile flow models and image-guided interventions in animal models, interventional cardiology, and interventional radiology. The US-guided, intravascular steerable robotic system will have significant societal impact through improved patient outcomes, reduced radiation exposure for the physician and the patient, reduced rate of procedural failures, and lower healthcare costs.